Various off-road and on-road vehicles include booms. For example, certain concrete pump trucks include a boom configured to support a passage through which concrete is pumped from a base of the concrete pump truck to a location at a construction site where the concrete is needed. Such booms may be long and slender to facilitate pumping the concrete a substantial distance away from the concrete pump truck. In addition, such booms may be relatively heavy. The combination of the substantial length and mass properties of the boom may lead to the boom exhibiting undesirable dynamic behavior. In certain booms in certain configurations, a natural frequency of the boom may be about 0.3 Hertz (i.e., 3.3 seconds per cycle). In certain booms in certain configurations, the natural frequency of the boom may be less than about 1 Hertz (i.e., 1 second per cycle). In certain booms in certain configurations, the natural frequency of the boom may range from about 0.1 Hertz to about 1 Hertz (i.e., 10 seconds per cycle to 1 second per cycle). For example, as the boom is moved from place to place, the starting and stopping loads that actuate the boom may induce vibration (i.e., oscillation). Other load sources that may excite the boom include momentum of the concrete as it is pumped along the boom, starting and stopping the pumping of concrete along the boom, wind loads that may develop against the boom, and/or other miscellaneous loads.
Other vehicles with booms include fire trucks in which a ladder may be included on the boom, fire trucks which include a boom with plumbing to deliver water to a desired location, excavators which use a boom to move a shovel, tele-handlers which use a boom to deliver materials around a construction site, cranes which may use a boom to move material from place-to-place, etc.
In certain boom applications, including those mentioned above, a hydraulic cylinder may be used to actuate the boom. By actuating the hydraulic cylinder, the boom may be deployed and retracted, as desired, to achieve a desired placement of the boom. In certain applications, counter-balance valves may be used to control actuation of the hydraulic cylinder and/or to prevent the hydraulic cylinder from uncommanded movement (e.g., caused by a component failure).
Conventional solutions for reducing the above mentioned oscillations are typically passive (i.e., orifices) which are tuned for one particular operating point and often have a negative impact on efficiency. Many machines/vehicles with extended booms employ counter-balance valves (CBVs) for safely and safety regulation reasons. These counter-balance valves (CBVs) restrict/block the ability of the hydraulic control valve to sense and act upon pressure oscillations. In certain applications, such as concrete pump truck booms, oscillations are induced by external sources (e.g., the pumping of the concrete) when the machine (e.g., the boom) is nominally stationary. In this case, the counter-balance valves (CBVs) are closed, and the main control valve is isolated from the oscillating pressure that is induced by the oscillations. There are a number of conventional solutions that approach this problem, that typically rely on joint position sensors to sense the oscillations (i.e., ripples) and prevent drift due to flow through a ripple-cancelling valve. Some solutions also have parallel hydraulic systems that allow a ripple-cancelling valve to operate while the counter-balance valves (CBVs) are in place.